Fluid storage and dispensing system including dynamic fluid monitoring of fluid storage and dispensing vessel

ABSTRACT

A monitoring system for monitoring fluid in a fluid supply vessel during operation including dispensing of fluid from the fluid supply vessel. The monitoring system includes (i) one or more sensors for monitoring a characteristic of the fluid supply vessel or the fluid dispensed therefrom, (ii) a data acquisition module operatively coupled to the one or more sensors to receive monitoring data therefrom and responsively generate an output correlative to the characteristic monitored by the one or more sensors, and (iii) a processor and display operatively coupled with the data acquisition module and arranged to process the output from the data acquisition module and responsively output a graphical representation of fluid in the fluid supply vessel.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fluid storage and dispensing systemincluding dynamic monitoring of inventory of a fluid storage anddispensing vessel.

2. Description of the Related Art

In the field of semiconductor manufacturing, involving unit operationssuch as ion implantation, chemical vapor deposition, spin-on coating,etching, cleaning of process chambers, treatment of effluents, etc., itis common to utilize specialized fluid reagents of widely varyingcharacter.

Due to the high costs, significant toxicity, and ultra-high purityrequirements of many of such fluid reagents, a variety of dedicatedsource vessels and containment apparatus have come into widespread usagein semiconductor manufacturing facilities. In many instances, thesespecialty fluid supply apparatus, which have replaced conventional gascylinders in such service, are accessorized with various fluidmonitoring and control devices. Such devices may for example includeleak detection monitors, pressure transducers in dispensing lines,temperature sensors for ensuring that contained and dispensed fluid isat an appropriate thermal state for the associated process operation,mass flow controllers, restricted flow orifice elements, and the like.

Among the most innovative and commercially successful of the currentgeneration of fluid storage and dispensing systems for semiconductormanufacturing reagents are those commercialized by ATMI, Inc. (Danbury,Conn.) under the trademarks SDS® and VAC®.

The SDS® fluid storage and dispensing system includes a vesselcontaining a solid-phase sorbent material having sorptive affinity forthe semiconductor manufacturing fluid reagent, whereby fluid stored inthe vessel on such sorbent material can be selectively desorbedtherefrom and dispensed from the vessel under dispensing conditions. Thesemiconductor reagent fluid can be stored at low pressure as a result ofits sorptive retention in the vessel, e.g., at subatmospheric pressures.As a result of such low pressure storage, a high level of safety isprovided, in relation to high pressure gas cylinders in which a valvehead failure can result in widespread dissemination of the fluidcontents of the cylinder. The SDS® fluid storage and dispensing systemis variously described in U.S. Pat. Nos. 5,518,528; 5,704,965;5,704,967; and 5,707,424.

The VAC® fluid storage and dispensing system includes a vesselcontaining a semiconductor manufacturing fluid reagent and equipped witha pressure regulator that is interiorly disposed in the vessel and inflow communication with a dispensing assembly for dispensing of fluid atpressure determined by the set point of the pressure regulator. Thepressure regulator set point can be set to a low dispensing pressurelevel. The VAC® fluid storage and dispensing system is variouslydescribed in U.S. Pat. Nos. 6,101,816; 6,089,027; 6,360,546; 6,474,076;and 6,343,476.

By its interior pressure regulator configuration, the VAC® fluid storageand dispensing system achieves an enhancement of safety in thecontainment of high pressure fluids, since the regulator prevents thedischarge of fluid at pressure above the regulator set point, and sincethe regulator is inside the vessel and thereby protected from ambientcontamination and direct impact.

In ion implant applications, the SDS® fluid storage and dispensingsystem has become a standard gas source in the semiconductormanufacturing industry. Currently, it is estimated that approximately80% of the installed base of 4000 ion implant units worldwide utilizethe SDS® fluid storage and dispensing system.

In order to assure proper utilization of the SDS® fluid storage anddispensing system, special consideration of the gas delivery systemdesign including low pressure drop components and accurate measurementof sub-atmospheric (torr-level) pressure is required. This poses aparticular problem in that there are a half dozen or so majormanufacturers of ion implant equipment. Each manufacturer makes severalmodel types and new products are released every 2-3 years. Thiscircumstance results in a wide variety of ion implant systems andsubsequently results in a myriad of gas monitoring techniques being inuse, many of which are inadequate or otherwise inefficient andunstandardized.

In one of the most popular current ion implant system designs, gasmonitoring of the inventory of fluid in the SDS® fluid storage anddispensing system requires navigating through a complex series ofsoftware files in order to determine pressure of the fluid in the SDS®fluid storage and dispensing vessel. The user then has to manuallyconvert the pressure into a unit of fluid utilization. The problem withthis approach is that the time required to navigate the software screensin this implementation is excessive, and most ion implant operators andtechnicians cannot understand the conversion mathematics required toconvert the pressure reading into a meaningful utilization expression.

The foregoing deficiencies in monitoring utilization of fluid stored fordispensing in the fluid supply vessel is exacerbated by the fact thatnumerous implanter units, e.g., 5-20, are provided in a typically-sizedsemiconductor manufacturing facility, or “fab.” The multiplicity of suchunits means that it often requires an operator or technician to spendhours in monitoring operations for all of the implanter units todetermine the rate and extent of fluid consumption by the ion implanter,or other dispensed fluid-using equipment in the semiconductor fab.

Another problem with conventional approaches to monitoring fluidutilization for determining consumption of the fluid in the fluid supplyvessel is that it is difficult to predict and alert fab personnel to theapproaching end-point of the dispensing operation, when the vessel isnearly depleted of its fluid contents and approaching exhaustion.

Since existing approaches to determination of utilization are poor, itis a not infrequent occurrence that fab personnel run out of fluidwithout warning during active implant operation. This occurrencetypically has a severe impact on fab productivity since the implant unitmust then be shut down to accommodate change-out of the depleted fluidsupply and dispensing vessel, and installation of a fresh vesselcontaining fluid for renewed operation. Since this occurrence isunscheduled, the efficiency with which the fluid storage and dispensingsystem can be replaced is less than if the event were scheduled or ableto be predicted.

There is therefore a significant need in the art for a fast, accurateand reliable approach to monitoring utilization and detecting end-pointdispensing conditions in the use of fluid storage and dispensing systemsof the above-described type.

SUMMARY OF THE INVENTION

The present invention relates generally to a system and method fordynamic monitoring of fluid in fluid storage and dispensing systems,such as those of the SDS®-type and the VAC®-type, to determineutilization of fluid in such systems.

In one aspect, the present invention relates to a monitoring system formonitoring fluid in a fluid supply vessel during operation includingdispensing of fluid from the fluid supply vessel, said monitoring systemincluding (i) one or more sensors for monitoring a characteristic of thefluid supply vessel or the fluid dispensed therefrom, (ii) a dataacquisition module operatively coupled to the one or more sensors toreceive monitoring data therefrom and responsively generate an outputcorrelative to the characteristic monitored by the one or more sensors,and (iii) a processor and display operatively coupled with the dataacquisition module and arranged to process the output from the dataacquisition module and responsively output a visual representation suchas a graph or audio signal, such as an alarm to denote the fluid in thefluid supply vessel.

In another aspect, the invention relates to a method of monitoring fluidin a fluid supply vessel during operation including dispensing of fluidfrom the fluid supply vessel, said method including (i) monitoring acharacteristic of the fluid supply vessel or the fluid dispensedtherefrom, (ii) acquiring data from said monitoring and responsivelygenerating an output correlative to the monitoring characteristic, and(iii) processing the output from the data acquiring and responsivelyoutputting a graphical representation of fluid in the fluid supplyvessel.

Other aspects, features and advantages of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an ion implanter utilizing anarrangement of fluid storage and dispensing vessels in the gas box ofthe implanter, in which fluid utilization is dynamically monitored by afluid monitoring system, according to one embodiment of the invention.

FIG. 2 is a schematic representation of the visual display interface ofa visual display unit of the fluid monitoring system shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED FEATURES THEREOF

The present invention provides a dynamic monitoring system and methodthat is usefully employed to monitoring fluid utilization in a fluidsupply system, such as the fluid storage and dispensing systems of thetypes described in the Background of the Invention section hereof.

The monitoring system includes (i) one or more sensors for monitoring acharacteristic of the fluid supply vessel or the gas dispensedtherefrom, (ii) a data acquisition module operatively coupled to the oneor more sensors, and (iii) a processing and display unit operativelycoupled to the data acquisition module for determining utilization ofthe fluid in the fluid supply vessel and responsively outputting agraphical representation of fluid in the fluid supply vessel.

The one or more sensors for monitoring a characteristic of the fluidsupply vessel in the dynamic fluid monitoring system of the inventionmay be of any suitable type, such as fluid sensors for sensing aselected characteristic of the fluid that is useful in determining theinventory and utilization rate of the gas. The selected characteristicof the fluid may for example include pressure of the fluid within thevessel or as it leaves the vessel, concentration of a specific componentof the fluid within the vessel or in connecting lines between the vesseland downstream processing unit, temperature of the fluid within thevessel or in connecting lines between the vessel and downstreamprocessing unit, flow rate of the fluid as the fluid leave the vessel orin connecting lines to the downstream processin unit, different mixtureof gases both in the vessel and in connecting lines leaving the vessel,flow rate of purging gases in the connecting lines between the vesseland downstream processing system, etc., and the corresponding sensorsmay variously include pressure transducers, manometric pressure sensors,thermocouples, mass flow controllers, flow totalizers, etc.

Alternatively, the one or more monitoring sensors in the dynamicmonitoring system of the invention may include one or more sensors fordetermining a characteristic of the fluid supply vessel itself, such asfor example strain on the vessel wall of the fluid supply vessel wherethe fluid is contained at high pressure in the vessel, e.g., a vesselsuch as that of the VAC® fluid supply system (ATMI, Inc., Danbury,Conn., USA) described earlier herein, wherein the fluid is confinedagainst a pressure regulator set to a predetermined set point pressurefor dispensing of fluid from the vessel. Alternatively, thecharacteristic of the fluid supply vessel that may be employed formonitoring in accordance with the invention can be temperature of thefluid supply vessel, displacement or flexial character of the vessel,weight of the fluid supply vessel containing the fluid being or to bedispensed, etc. Still further, other devices that may be monitoredinclude any pressure-reducing device that has a net effect in decreasingthe interior pressure of a cylinder thereby reducing downstreampressure, such as restrictive flow orifice. Thus, by monitoring thistype of device the operator would be assured that delivery pressuresremained fixed and gas flow rates more closely matched the actualprocess needs downstream.

The processing and display unit that is coupled to the data acquisitionmodule may utilize any suitable processing means, e.g., a generalpurpose programmable digital computer or central processing unit (CPU)including memory and processor components. The processor may be arrangedto communicate with the memory by means of an address/data bus, and canbe constituted by a commercially available or custom microprocessor. Thememory can include, without limitation, devices of varied type, such ascache, ROM, PROM, EPROM, EEPROM, flash memory, SRAM, and DRAM.

The memory may include several categories of software and data used inthe data processing system: the operating system; the applicationprograms; the input/output (I/O) device drivers and the data. The datamay include a database of known profiles of fluid storage and dispensingvessel characteristics, characteristics of various fluids, historicaloperating data for the gas-utilizing equipment being supplied with gasfrom the fluid storage and dispensing system, etc.

It will be appreciated that the operating system in the processing anddisplay unit can be of any suitable type for use with a data processingsystem. Illustrative examples of operating systems that can be usefullyemployed include, without limitation, OS/2, AIX, OS/390 or System390(International Business Machines Corporation, Armonk, N.Y.), Windows CE,Windows NT, Windows95, Windows98, Windows2000, or WindowsXP (MicrosoftCorporation, Redmond, Wash.), Unix or Linux or FreeBSD, Palm OS fromPalm, Inc., Mac OS (Apple Computer, Inc.), LabView or proprietaryoperating systems.

The I/O device drivers typically include software routines accessedthrough the operating system by the application programs to communicatewith devices such as I/O data port(s), data storage and certaincomponents of the memory.

The application programs are illustrative of the programs that implementthe various features of the system and can suitably include one or moreapplications that support analysis of the data. The data represent thestatic and dynamic data used by the application programs, the operatingsystem, the I/O device drivers, and other software programs that mayreside in the memory.

Any configuration of the processor capable of carrying out theoperations for the methodology of the invention can be advantageouslyemployed.

The I/O data port of the processing and display unit can be used totransfer information between the processing and display unit and anothercomputer system or a network (e.g., the Internet) or to other devicescontrollable by the processor.

The processing and display unit includes a display for graphicallyoutputting the fluid utilization of the vessel(s) being monitored, e.g.,in the form of a representation of the vessel(s) being monitored and itsfluid content. This representation may be a “gas gauge” type of graphicdepiction, in which the fluid content is shown in scale to the vesselschematically depicted in the graphical output, as a two-dimensionalcolumn having an upper bounding line representing the volumetric contentof the fluid in the vessel, in which the upper bounding line isvertically downwardly translated in the display as the fluid isdispensed from the vessel and consumed in the external fluid-consumingfacility that is being supplied with fluid from the vessel. Such type ofdepiction of the “fill status” of the vessel provides an intuitive andreadily visually perceptible indication of the inventory of the fluidremaining in the vessel.

In a specific embodiment, the dynamic monitoring system of the inventionmay be employed to monitor an SDS® gas supply system, by monitoringpressure signals from pressure transducers operatively arranged todetect the pressure characteristic of gas being dispensed from the SDS®vessel. In another specific embodiment, the dynamic monitoring systemmay be employed to monitor a VAC® gas supply system, by monitoring astrain gauge on the VAC® vessel inside an ion implanter. Thesensor-derived signals then are sent to the data acquisition module,from which send signals can be sent via a signal transmission line,e.g., a fiber optic communications link, to the processing and displayunit, for display and archiving of the data in a nonvolatile buffer.

In another embodiment, the processing and display unit may alsoincorporate or be linked to alarming means, such as for example lowpressure alarms indicating that the fluid storage and dispensing vesselis approaching a depletion end point.

The data acquisition module and the processing and display unit may beconstructed and arranged to monitor multiple fluid supply and dispensingvessels, such as an array of such vessels in the gas box of an ionimplanter in a fab.

The processing and display unit is suitably configured in one embodimentof the invention to calculate remaining usable volume of fluid in afluid supply vessel based on known isotherm equations, vessel size andfluid type. This is highly advantageous because the volume of fluidremaining in a fluid supply vessel as it approaches exhaustion is notlinear with pressure. As an illustrative example, with 100 torr of fluidpressure remaining in a 2.2 L AsH₃ SDS® cylinder, 50% of the deliverablearsine still remains in the vessel.

Referring now to the drawings, FIG. 1 is a schematic representation of afab installation 10 including an ion implanter 12 utilizing anarrangement of fluid storage and dispensing vessels 22, 24, 26 and 28 inthe gas box 14 of the implanter, in which fluid utilization isdynamically monitored by a fluid monitoring system, according to oneembodiment of the invention.

As schematically illustrated, the ion implanter 12 includes acontainment structure defining an interior volume 16 containing the gasbox 14. The gas box in turn defines an interior volume 18 in which isdisposed an array of fluid storage and dispensing vessels 22, 24, 26 and28, each of which has an associated pressure transducer (“PT”), e.g.,disposed in a valve head of the vessel assembly and arranged to sensethe fluid pressure of fluid dispensed from the associated vessel.

The pressure transducers associated with the vessels 22, 24, 26 and 28generate signals correlative to the sensed pressure in each dispensingoperation (the flow circuitry associated with the fluid supply anddispensing vessels, and the details of the ion implantation apparatus inthe ion implanter containment structure not being shown, for ease ofdescription) and such signals are transmitted by the signal transmissionlines 30, 32, 34 and 36 to the data acquisition module 40.

The data acquisition module 40 serves to acquire the sensing signalsfrom the sensors associated with the vessels and process the signalsinto a suitable form for transmission to the processor and display unit50 by means of signal transmission line 48, such as a fiber optic cable,extending from the data acquisition module 40 through the wall of thegas box 14 and the enclosing wall of the ion implanter 12, to theprocessor and display unit 50. Notably, in the alternative, theacquistion module can receive the sensing signals remotely via awireless communications means such as a device that transmits via radiofrequency.

The data acquisition module 40 serves to acquire the sensing signalsfrom the sensors associated with the vessels and process the signalsinto a suitable form for transmission to the processor and display unit50 by means of signal transmission line 48, such as a fiber optic cable,extending from the data acquisition module 40 through the wall of thegas box 14 and the enclosing wall of the ion implanter 12, to theprocessor and display unit 50. Notably, in the alternative, theacquistion module can receive the sensing signals via a wirelesscommunications means such as a device that transmits via radiofrequency.

The processor and display unit 50 includes signal processing means aspreviously described herein, which processes the signals transmitted bythe signal transmission line 48 to produce a graphical output that isdisplayed on the display 52 of the unit 50. The processor and displayunit 50 is powered by a suitable power supply, e.g., by a power cord 54operatively coupled with a transformer 56, e.g., a 12 volt walltransformer, and adapted for plug-in to a wall socket of an electricalsupply network, e.g., a 110-volt or 220-volt service.

FIG. 2 is a schematic representation of the visual display interface ofthe visual display unit 50 of the fluid monitoring system in the fabinstallation 10 shown in FIG. 1.

As illustrated, the visual display interface shows graphical depictionsof each of the four vessels 22, 24, 26 and 28 in the gas box 14 of theinstallation 10, in the form of two-dimensional vertically extendingrectangles having a horizontal line depicting the boundary of the fluidinventory in each rectangle.

In the specific example shown, the fluid inventory is shown by a white“fill volume” which in relation to the total area of the associatedrectangle indicates the amount of the fluid remaining in the vessel atany given time. By such output, the status of each of the monitoredvessels is readily apparent at a glance, as to its fluid inventory. Thedisplay may also, as in the illustrative display shown in FIG. 2, alsoprovide a numerical indication of the relative fluid filled state of therespective vessels (e.g., as shown by the numerical indicia “93”, “123”,“40” and “91” in the display depicted in FIG. 2).

The monitoring process may be carried out in any suitable manner, asregards transmission of sensed data to the data acquisition module 40,for monitoring in a real-time, continuous fashion as desired in a givenapplication of the invention.

Regarding specific embodiments of the dynamic monitoring system shown inFIG. 1 and FIG. 2, the processor and display unit may be equipped forinterfacing with a computer, e.g., in an operator station in the fab.The processor and display unit may for example be equipped with anRS-232 port for such purpose, to enable cabling between such RS-232 porton the processor and display module, and a serial port on an operatorcomputer. The data acquisition module may be suitably configured forproviding sensor excitation and analog input for each of the sensorsassociated with the vessels. When the sensors are strain gauges mountedon the walls of the fluid storage and dispensing vessels, such sensorsmay be readily cabled to the data acquisition module.

The processor and display unit in a specific embodiment is arranged fordata logging with archiving of up to 3000 data points, with loggingrates configured from a setup menu to a suitable value in a range offrom 5 seconds per point to 2 hours per point. All four channels for thefour vessels in the illustrative installation are logged and loggingdata is downloadable through an RS-232 port of the processor and displayunit. A trend graph may be provided for each of the four monitoredchannels, scaled to match the bar graph 100% (indicating complete fluidinventory in the vessel) and to show the entire data log buffer. Sincethe display is 100 points wide and the data log is 3000 points wide, thedisplay shows an average of 300 readings per pixel on the display. Forfiner viewing, data may be downloaded from the processor and displayunit via the RS232 port. The processor and display unit in a specificembodiment is configured so that each data element is time stamped bythe processor.

The features, operation and advantages of the invention are more fullydescribed with reference to the following non-limiting example of anillustrative embodiment of the invention.

EXAMPLE

This example illustrates the procedures used to estimate the usable gasin a gas storage and dispensing system of a type commercially availableunder the trademark SDS2 from ATMI, Inc. (Danbury, Conn.) and more fullydescribed in U.S. Pat. Nos. 5,518,528; 5,704,965; 5,704,967; and5,707,424. Such gas storage and dispensing system includes a gas storageand dispensing vessel containing a bead activated carbon adsorbenthaving sorptive affinity for the semiconductor manufacturing gas held inthe interior volume of the vessel. The gas may be of any suitable type,e.g., arsine, phosphine, boron trifluoride, germanium tetrafluoride, andsilicon tetrafluoride, and the gas may be retained in the vessel fordispensing therefrom at suitable pressure, e.g., a subatmosphericpressure in a range of 200 to 700 torr.

The illustrative gas storage and dispensing system is deployed in an ionimplanter of the type schematically shown in FIG. 1 hereof, equippedwith a dynamic fluid utilization monitoring system of the invention. Thedynamic fluid monitoring system in this embodiment includes a processingand display unit, a data acquisition module, and fluid sensors forsensing a selected characteristic of the fluid that may be used todetermine the inventory and utilization rate of the gas. The fluidsensors in this embodiment include pressure transducers, each of whichis operatively coupled with one of the multiple gas storage anddispensing vessels as schematically shown in FIG. 1.

The processing and display unit is programmably arranged to estimate theamount of usable gas remaining in the SDS2 vessel at a given pressureand temperature. The dynamic monitoring system of the invention can beused to estimate the service life of a gas storage and dispensing vesselused in the implanter.

In the utilization determination, the following symbols and units areemployed.

-   T Gasbox temperature, ° C.-   P Pressure transducer reading, torr or mmHg-   P₂₁ Normalized pressure reading, torr or mmHg-   P_(end-21) Normalized end point pressure, torr or mmHg-   C_(lo) Pressure change per degree ° C. when temperature is less than    21° C., torr/° C.-   C_(mid) Pressure change per degree ° C. when temperature is between    21-26° C., torr/° C.-   C_(hi) Pressure change per degree ° C. when temperature is less than    26-33° C., torr/° C.-   C_(end-lo) Pressure change per degree ° C. for end point pressure    (less than 21° C.), torr/° C.-   C_(end-mid) Pressure change per degree ° C. for end point pressure    (21-26° C.), torr/° C.-   C_(end-hi) Pressure change per degree ° C. for end point pressure    (26-33° C.), torr/° C.-   CW Carbon weight in the cylinder, gram-   MW Molecular weight of the gas-   sccm Gas flow rate to the ion source, ml/min-   G The amount gas in grams remained in the cylinder, gram-   V The amount gas in cubic centimeter remained in the cylinder, ml-   HR Number of hours left before the cylinder is empty, hour.-   4x 2.2 liter SDS® cylinder, also called JY size-   7x 0.4 liter SDS® cylinder, also called WY size-   3x 6.6 liter SDS® cylinder, also called UY size

The utilization determination is carried out by the following steps:

Step 1: Measure or determine the implanter gasbox temperature T (° C.)

Step 2: Determine the gas storage and dispensing vessel size and weightof sorbent material therein. For example, the vessel size may be 4x, 7xor 3x. The sorbent then may have a carbon sorbent material disposed inthe vessel, having a carbon weight (CW) in grams, which is dependent onthe vessel size. If the vessel size is 4x, then the CW is 1275. If thevessel size is 7x, then the CW is 239. If the vessel size is 3x, thenthe CW is 3825.

Step 3: Set the end-point pressure P_(end) of the fluid storage anddispensing system, e.g., an end-point pressure P_(end) of 5 torr.

Step 4: Measure the vessel pressure reading, P.

Step 5: Determine the temperature coefficients, dP/dT, at variouspressures.

For example:

-   -   If T is less than 21° C.:        C _(lo)=0.04079168*(P ^(^0.9623277))    -   If T is between 21 to 26° C.:        C _(mid)=0.07282172*(P ^(^0.8938195))    -   If T is less than 26 to 33° C.:        C _(hi)=0.08678193*(P ^(^0.8914468))

Step 6: Determine the temperature coefficient for the end pointpressure.

For example:

-   -   If T is less than 21° C.:        C _(end-lo)=0.04079168*(P _(end) ^(^0.9623277))    -   If T is between 21 to 26° C.:        C _(end-mid)=0.07282172*(P _(end) ^(^0.8938195))    -   If T is less than 26 to 33° C.:        C _(end-hi)=0.08678193*(P _(end) ^(^0.8914468))

Step 7: Normalize the pressure reading to a predetermined temperature,e.g., 21° C.

For example:

-   -   If T is less than 21° C.:        P ₂₁=P−(T−21)*C _(lo)    -   If T is between 21 to 26° C.:        P ₂₁=P−(−21)*C _(mid)    -   If T is between 26 to 33° C.:        P ₂₁=P−(T−21)*C _(hi)

Step 8: Normalize the end point pressure to the predeterminedtemperature (21° C.).

For example:

-   -   If T is less than 21° C.:        P _(end-21)=P _(end)−(T−21)*C _(end-lo)    -   If T is between 21 to 26° C.:        P _(end-21)=P _(end)−(T−21)*C _(end-mid)    -   If T is between 26 to 33° C.:        P _(end-21)=P _(end)−(T−21)*C _(end-hi)

Step 9: Determine isotherm equations at the predetermined temperature(21° C.).

For example, for various illustrative gases:

isotherm equations at 21° C.:AsH₃ Capacity (g/g): f(P)=−0.40857+0.14009*(ln(P+24.5858))PH₃ Capacity (g/g): f(P)=−0.29123+0.06949*(ln(P+73.89104))BF₃ Capacity (g/g): f(P)=0.03949+0.00532*(P ^(^0.49046))GeF₄ Capacity (g/g): f(P)=0.2394*(P ^(^0.2139))SiF₄ Capacity (g/g): f(P)=−0.60234+0.1223*(ln(P+160.6716))wherein g/g is the gram of gas per gram of carbon, and P is the pressurein torr or mmHg.

Step 10: Determine the amount of gas remaining in the fluid storage anddispensing vessel.

For example:

-   -   Weight: Grams of gas remaining in the cylinder (g):        G=CW*f(P ₂₁)−f(P _(end-21))    -   Volume: Cubic Centimeter of Gas remained in the cylinder (ml):        V=(G/MW)*22400        where AsH₃: MW=78    -   PH₃: MW=34    -   BF₃: MW=68    -   GeF₄: MW=149    -   SiF₄: MW=104    -   Cylinder life time: Working hours of the cylinder remaining        (hr):        HR=(V/sccm)/60        wherein sccm is the gas flowrate into the ion source (e.g., 2        ml/min)

The foregoing methodology permits the dynamic monitoring of the gasinventory of the fluid storage and dispensing system in a ready,accurate and reproducible manner, that is outputted by the visualdisplay module in a manner illustrated in FIG. 2 hereof, wherein thevertical height of the fluid column on the visual display is indicativeof the amount of fluid remaining in the storage and dispensing vessel ofsuch system.

It will therefore be seen that the system and method of the presentinvention permit a simple visually perceptible indication of the fluidinventory of vessels in a fluid storage and dispensing system, which issimply and easily applicable to the dynamic monitoring of fluid insupply vessels in a gas box of an ion implanter. The invention overcomesthe problems of the prior art including the inability to determine withprecision the amount of fluid remaining in vessels for activeprocessing, and the approach to exhaustion of fluid in the fluid supplyvessels.

As a result, the system and method of the invention permit the uptime ofan ion implanter to be maximized, and the change-out of fluid supplyvessels to be accurately predicted and scheduled.

Although the invention has been described herein with reference toillustrative features, aspects and embodiments, it will be appreciatedthat the invention may be practiced with modifications, variations andin other embodiments, as will suggest themselves to those of ordinaryskill based on the disclosure herein. The invention therefore is to beinterpreted and construed, as encompassing all such modifications,variations, and other embodiments, within the spirit and scope of theclaims hereafter set forth.

1. A monitoring system for monitoring fluid in a fluid supply vessel in a gas box of an ion implanter during operation including dispensing of fluid from the fluid supply vessel, said monitoring system including (i) one or more sensors for monitoring a characteristic of the fluid supply vessel or the fluid dispensed therefrom, (ii) a data acquisition module operatively coupled to the one or more sensors to receive monitoring data therefrom and responsively generate an output correlative to the characteristic monitored by the one or more sensors, and (iii) a processor and display operatively coupled with the data acquisition module and arranged to process the output from the data acquisition module and responsively output a graphical representation of fluid in the fluid supply vessel, said processor and display being operatively coupled with the data acquisition module by a fiber optic cable from the data acquisition module extending through a wall of the gas box and an enclosing wall of the ion implanter to the processor and display.
 2. The monitoring system of claim 1, wherein said one or more sensors monitor a characteristic of the fluid supply vessel.
 3. The monitoring system of claim 2, wherein the characteristic of the fluid supply vessel is strain in a structural component of the vessel.
 4. The monitoring system of claim 3, wherein the structural component of the vessel comprises a wall of the vessel.
 5. The monitoring system of claim 3, wherein the one or more sensors comprise a strain gauge.
 6. The monitoring system of claim 4, wherein the one or more sensors comprise a strain gauge secured in strain-sensing relationship to the vessel wall.
 7. The monitoring system of claim 1, wherein said one or more sensors monitor a characteristic of fluid dispensed from the fluid supply vessel.
 8. The monitoring system of claim 7, wherein said characteristic of fluid dispensed from the fluid supply vessel comprises at least one of fluid characteristics selected from the group consisting of fluid pressure, fluid temperature, concentration of one or more components of the fluid, flow rate of the fluid, pressure drop in flow circuitry coupled with the fluid supply vessel, and cumulative flow rate of the fluid dispensed from the fluid supply vessel.
 9. The monitoring system of claim 7, wherein said characteristic of fluid dispensed from the fluid supply vessel comprises fluid pressure.
 10. The monitoring system of claim 1, wherein the fluid supply vessel contains a sorbent medium having sorptive affinity for the fluid.
 11. The monitoring system of claim 1, wherein the fluid supply vessel includes a pressure regulator interiorly disposed in the vessel and set to a set point for dispensing of fluid from the vessel.
 12. The monitoring system of claim 11, wherein the set point of the pressure regulator is a subatmospheric pressure set point.
 13. The monitoring system of claim 1, wherein the fluid supply vessel contains a semiconductor manufacturing fluid.
 14. The monitoring system of claim 13, wherein the semiconductor manufacturing fluid comprises a fluid component selected from the group consisting of arsine, phosphine, boron trifluoride, germanium tetrafluoride, and silicon tetrafluoride.
 15. The monitoring system of claim 1, wherein the graphical representation of fluid in the fluid supply vessel comprises a two-dimensional area with an upper boundary line, disposed in a rectangular field wherein the position of the upper boundary line of the two-dimensional area in the field indicates fluid inventory in the vessel.
 16. The monitoring system of claim 1, wherein the graphical representation of fluid in the fluid supply vessel comprises a gas tank type gauge.
 17. The monitoring system of claim 1, further comprises a pressure reducing device that has a net effect in decreasing the interior pressure of a cylinder thereby reducing downstream pressure.
 18. The monitoring system of claim 17, wherein the pressure-reducing device is a flow restrictive orifice.
 19. A method of monitoring fluid in a fluid supply vessel in a gas box of an ion implanter during operation including dispensing of fluid from the fluid supply vessel, said method including (i) monitoring a characteristic of the fluid supply vessel or the fluid dispensed therefrom, (ii) acquiring data from said monitoring via a data acquisition module and responsively generating an output therefrom that is correlative to the monitoring characteristic, and (iii) processing the output from the data acquiring and responsively outputting a graphical representation of fluid in the fluid supply vessel via a processor and display, said processor and display being operatively coupled with the data acquisition module by a fiber optic cable from the data acquisition module extending through a wall of the gas box and an enclosing wall of the ion implanter to the processor and display.
 20. The method of claim 19, wherein said characteristic comprises a characteristic of the fluid supply vessel.
 21. The method of claim 19, wherein the characteristic comprises strain in a structural component of the vessel.
 22. The method of claim 21, wherein the structural component of the vessel comprises a wall of the vessel.
 23. The method of claim 21, wherein the monitoring comprises sensing strain by a strain gauge.
 24. The method of claim 19, wherein said characteristic comprises a characteristic of fluid dispensed from the fluid supply vessel.
 25. The method of claim 24, wherein said characteristic of fluid dispensed from the fluid supply vessel comprises at least one of fluid characteristics selected from the group consisting of fluid pressure, fluid temperature, concentration of one or more components of the fluid, flow rate of the fluid, pressure drop in flow circuitry coupled with the fluid supply vessel, and cumulative flow rate of the fluid dispensed from the fluid supply vessel.
 26. The method of claim 24, wherein said characteristic of fluid dispensed from the fluid supply vessel comprises fluid pressure.
 27. The method of claim 19, wherein the fluid supply vessel contains a sorbent medium having sorptive affinity for the fluid.
 28. The method of claim 19, wherein the fluid supply vessel includes a pressure regulator interiorly disposed in the vessel and set to a set point for dispensing of fluid from the vessel.
 29. The method of claim 28, wherein the set point of the pressure regulator is a subatmospheric pressure set point.
 30. The method of claim 19, wherein the fluid supply vessel contains a semiconductor manufacturing fluid.
 31. The method of claim 30, wherein the semiconductor manufacturing fluid comprises a fluid component selected from the group consisting of arsine, phosphine, boron trifluoride, germanium tetrafluoride, and silicon tetrafluoride.
 32. The method of claim 19, wherein the graphical representation of fluid in the fluid supply vessel comprises a two-dimensional area with an upper boundary line, disposed in a rectangular field wherein the position of the upper boundary line of the two-dimensional area in the field indicates fluid inventory in the vessel.
 33. The method of claim 19, wherein the graphical representation of fluid in the fluid supply vessel comprises a gas tank type gauge.
 34. A monitoring system for monitoring fluid in a fluid supply vessel during operation including dispensing of fluid from the fluid supply vessel, said monitoring system including (i) one or more sensors for monitoring a characteristic of the fluid supply vessel or the fluid dispensed therefrom, (ii) a data acquisition module operatively coupled to the one or more sensors to receive monitoring data therefrom and responsively generate an output correlative to the characteristic monitored by the one or more sensors, and (iii) a processor and display operatively coupled with the data acquisition module and arranged to process the output from the data acquisition module and responsively output a graphical representation of fluid in the fluid supply vessel deployed in an ion implanter, wherein the fluid supply vessel comprises a gas storage and dispensing vessel containing activated carbon adsorbent and a semiconductor manufacturing gas on the activated carbon adsorbent, wherein the gas storage and dispensing vessel is in a gas box of the ion implanter, wherein the one or sensors comprise a pressure transducer in the gas box, arranged to monitor pressure of gas dispensed from the gas storage and dispensing vessel, wherein the data acquisition module is in the gas box and arranged to receive pressure monitoring data from the pressure transducer, wherein the processor and display is outside of the ion implanter, and is operatively coupled with the data acquisition module by a fiber optic cable from the data acquisition module extending through a wall of the gas box and an enclosing wall of the ion implanter to the processor and display, and wherein the processor and display is programmably arranged to determine an amount of gas remaining in the gas storage and dispensing vessel and output a visual display of such remaining gas.
 35. The monitoring system of claim 34, wherein the processor and array is adapted to: determine a temperature coefficient for a predetermined endpoint pressure of gas dispensed from the gas storage and dispensing vessel; normalize pressure sensed by said pressure transducer to a predetermined temperature of the gas box; normalize the endpoint pressure to said predetermined temperature; and apply isotherm equations at said predetermined temperature, to determine the amount of gas remaining in the gas storage and dispensing vessel. 